CFRC is mainly produced by a chemical vapor deposition (hereinafter referred to as "CVD") method or a liquid phase impregnating method.
The CVD method comprises contacting hydrocarbon gas with a carbon fiber substrate heated to a high temperature under reduced pressure to deposit carbon atoms on the substrate. The liquid phase impregnating method comprises impregnating a matrix material such as a liquid resin or melt pitch in a carbon fiber substrate and calcining the impregnated substrate to carbonize the matrix material Since a volatile component of the matrix is removed from the substrate during calcination so that micropores are formed in the substrate, it is necessary to repeat impregnation and calcination in order to strengthen it.
The CVD method and the liquid phase impregnating method require lengthy complex steps, which is one of the for expensiveness of CFRC. Therefore, CFRC is not widely used except some fields where the cost is not significant, for example, the aerospace industry although it has an excellent properties such as good strength at a high temperature and chemical stability.
Recently, a carbon material not reinforced by the carbon fiber is conveniently produced without using any liquid matrix by directly calcining the carbon powder to carbonize to. Since a heat treated matrix is used, and therefore a total amount of the volatile materials is decreased, the carbon material with high density is advantageously produced. It could be expected that if the carbon powder were calcined together with the carbon fiber substrate, CFRC could be easily produced. However, it is difficult to homogeneously mix the carbon powder with the carbon fiber substrate so that good CFRC cannot be produced.
Instead of directly mixing the carbon powder with the carbon fiber substrate, the carbon powder may be dispersed in a liquid to form a slurry, impregnated in the carbon fiber substrate and then dried. By this slurry method, the impregnated amount of the carbon powder is not controlled, and the powder tends to be eliminated during drying. If a concentration of the slurry is high, a sufficient amount of the slurry is not impregnated in the substrate. If it is low, a sufficient amount of the carbon powder is not contained in the fiber although the slurry easily penetrates in the fiber. Further, the carbon powder is not strongly adhered to the carbon fiber substrate.